OF PHILADELPHIA. 411 



of the tip of the abdomen and of the thorax, which arrests the 

 attention when the insect is on the wing. [41] 



But it varies much in color. The vittae of the abdomen are 

 more or less dilated, sometimes hardly visible ; the head and 

 thorax are, in some individuals pearlaceous-blue, and the ultimate 

 abdominal segment varies from dull yellowish, with blackish lines, 

 to a bright pearl-blue, sometimes dull-yellowish with a pearlace- 

 ous-blue lateral spot on each. 



It is very common. 



The female has two small angulated processes beneath the tail, 

 which do not extend beyond the tip of the abdomen, the nails at 

 their extremities are curved downwards ; the hooks at the tip of 

 abdomen of the male are not obvious. 



The description is from recent specimens. The fine blue color 

 disappears in the cabinet specimens. 



B^TIS Leach. 



1. B. INTERPUNCTATA. — Whitish J head greenish; segments 

 of the tergum black on the posterior edges. 



Inhabits Indiana. 



Body yellowish-white, tinged with green ; head rather promi- 

 nent, yellow-green ; vertex with a lateral black point ; eyes with 

 a longitudinal black line ; stemmata distant, each with a black 

 orbit ; anterior one less than half the size of the others ; seta of 

 the antennae black ; front with a black angular line under the 

 antennae; neck distinct, separating the head from the trunk, with 

 a black line each side ; thorax somewhat brownish ; wings on the 

 anterior margin greenish, with black cross nervures, and a dis- 

 tinct, black, abbreviated, longitudinal [42] line on the middle, 

 between the third and fourth nervures ; feet greenish ; anterior 

 and intermediate pairs of thighs biannulate with blackish, poste- 

 rior pair tipped with dusky ; tergum with the posterior edge of 

 the incisures black; setae immaculate. 



Length nearly three-tenths of an inch. 



The small black spot on the middle of the costal margin is very 

 obvious. The abdomen at tip is more or less obviously ferru- 

 ginous. 



1839.] 



